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Calculating the number of night time hours, by day, in a year
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30-11-2020 6:54pm#1My first post over here
The context is calculating the dusk to dawn hours on a lighting project, incorporating the ESB 9 night rate hours from 12:00 to 9 summer time and 11pm to 8am winter time. day tae can be twice night rate so has a big impact on energy saving payback math.
So mid winter say
SR: 8:30
SS: 16:30
So 30 minutes and 4.5hrs at the day rate.
Midsummer
SR: 05:00
SS: 22:00
so all at night rate.
The web tells me 4,100 hrs but I would prefer some math to back it up.
Is there a site that has SR/SS by day by latitude?
Thanks“I can’t pay my staff or mortgage with instagram likes”.
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Comments
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Calahonda52 wrote: »My first post over here
The context is calculating the dusk to dawn hours on a lighting project, incorporating the ESB 9 night rate hours from 12:00 to 9 summer time and 11pm to 8am winter time. day tae can be twice night rate so has a big impact on energy saving payback math.
So mid winter say
SR: 8:30
SS: 16:30
So 30 minutes and 4.5hrs at the day rate.
Midsummer
SR: 05:00
SS: 22:00
so all at night rate.
The web tells me 4,100 hrs but I would prefer some math to back it up.
Is there a site that has SR/SS by day by latitude?
Thanks
https://www.timeanddate.com/sun/ireland/dublin
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Calahonda52 wrote: »Okay, am working through the math and have a problem added time in excel.
Adding these two rows
darkness = 24:00:00 minus (SS-SR)
..................SR............SS.......Darkness
30/12/20...08:40.......16:15.......16:24
31/12/20...08:40.......16:16.......16:23
................................................8:48 @ sum gives me this with format of h:mm
Thanks as always
ps
formatted the 16:xx's as a number, added them and the multiple by 24 works: 32.8
Works fine with this as the formula:
As you say, you can format the result as a number and it gives you a day fraction. Multiply by 24 if you want hours etc.0 -
Great, thanks, as that is more readable for my boss to check the math.
Anyway for what it is worth, here is the results:
ESB use 4,150 hrs as the dawn to dusk run hours for public lighting, the circuits are unmetered, so its the number of fittings by wattage by 4,150 by a rate per kW
When, for businesses, doing dusk to dawn payback math on going from halogens or SONs to LEDs, up to now we have just done 4,150 by the night rate, assuming they have night rate meter.
However day rate can be twice the night rate so the numbers below transform the payback math
2,624...... hours at night rate.... 61%
1,666...... Hours at day rate...... 39%
4,290...... Total darkness
there a more detailed summary in the attachment, I can't paste it in
“I can’t pay my staff or mortgage with instagram likes”.
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